regex to check all digits in are same or not

Question

I have input field which takes 12 digits number. I want to throw error when user enters 12 digits same number. Atleast one number has to be different.

E.g

   111111111111 - Error

   111111111112 - Ok

   123456789012 - Ok

I tried this (but i want inverse of the specified regex )

var pattern = "^([0-9])\\1{3}$";
var str = "5555";
pattern = new RegExp(pattern);
if(!pattern.test(str))
{
    alert('Error');
}
else
{
    alert('Valid');
}

code from : https://stackoverflow.com/a/2884414/1169180

Fiddle : http://jsfiddle.net/wn9scv3m/10/

Edit: No manipulation in if(!pattern.test(str)) in this line is allowed

Answer 1

You can use this regex:

^(\d)(?!\1+$)\d{11}$

RegEx Demo

---

Explanation:

• ^ - Match line start
• (\d) - match first digit and capture it in back reference #1 i.e. \1
• (?!..) is a negative lookahead
• (?!\1+$) means disallow the match if first digit is followed by same digit (captured group) till end.
• \d{11}$ match next 11 digit followed by line end